Method and means for the production of nonmetallic printing plates



March 30, 1937. o. BI CROWELL Y 2,075,507

METHOD AND MEANS FOR THE PRODUCTION OF NONMETALLIC PRINTING PLATES Filed Nov. 24, 1954 Patented Mar. 30, 1937 PATENT OFFEQE METHOD AND MEANS FOR, THE PRO- DUCTION OF NONMETALLIC PRINTING PLATES Orby B. Crowell, Toronto, Ontario, Canada, as-

signor to Viceroy Manufacturing Company,

Limited, Toronto, Ontario, Canada Application November 24, 1934, Serial No. '754,592

4 Claims.

The principal objects of this invention are to provide means for the rapid and effective production of flexible non-metallic printing plates, which Will be true replicas of a Wide variety of 5 original engravings or type forms and which, be-

cause of their exibility, may be capable of being mounted instantaneously on the cylinders of rotary presses or may be mounted on flat printing surfaces.

l A further and important object is to enable the production of flexible plates for use in multi-color printing which Will maintain accurate register when used in multi-color sets.

The principal features of the invention conl sist in the novel combination of materials and the method of making the mould from which the printing plates are fashioned, whereby an accurate reproduction of the original metal plates or type is effected, the plastic material which assumes the contours of the printing surface being reinforced with a material compounded there- With or introduced thereinto which will obviate excessive expansion and substantially eliminate shrinkage, thereby ensuring the reproduction of the original type surface in substantially its original dimensions.

In the accompanying drawing, Figure 1 is a perspective view oi a mould constructed in accordance with this invention.

Figure 2 is a diagrammatic sectional elevation illustrating the manner of compressing the material to form the mould around the contours of the original engraving type, or other plate or printing surface.

Figure 3 is an enlarged sectional detail of a portion of a mould constructed in accordance with this invention.

Figure 4 is an enlarged sectional detail of a portion of a mould constructed in accordance with this invention, but of a slightly modified form.

In the printing art it is quite old to produce rubber stamps or printing type in block or sheet form, the surface of which is moulded from va- 5 rious forms of solidifying plastics, or ductile metals such as plaster of Paris, synthetic resins, lead, lead alloys, etc., but such methods are subject to objectionable variations in dimensions due to the expansion and contraction of the materials used through the effect of the heat applied or to the evaporation of liquids therefrom. Further, such matrix or mould materials are objectionable because they key into the etched or engraved sides of the standing letters, lines or iigures on engraved plates and thereby render it difcult or impossible to part the mould or matrix from said plates Without breaking down, chipping o-r distorting the edges.

In carrying the present invention into effect, 5 the engraving I or other impression surface which it is desired to be reproduced in a flexible printing surface, is placed upon the bed of a suitable press. Over this surface l is placed a sheet 2 of rubber material of the desired quality, which l0 under predetermined pressure and temperature will reproduce the impression surface of the plate in a matrix which will later effectively mould the rubber material from which the ultimate printing plate is formed. The rubber material l5 from which the mould is formed is preferably compounded with a suitable cotton or other vegetable or mineral fibres 3 or mineral in ilake form, which reinforce and impart to the vulcanized mould properties of essential resistance to dis- 20 tortion, expansion or contraction incident to the temperatures and pressures used in the process of moulding the printing plates.

A modification of the non-shrinking reinforcement may be usedin which the bre or flake ma- 25 terials'are supplemented by a sheet of wire screen, or expanded or perforated metal, which may be embedded in the back of the body of rubber material forming the matrix or mould.

It will be apparent that the fine hairlike bres 30 will be uniformly distributed throughout the entire mass or body of the compound from which the mould is formed and will present an effective bonding structure against stressesl in all directions and where-the Wire screen or expanded metal is incorporated in conjunction therewith the fibres Will 'effectively interlock therewith due to their complete permeation of the entire mass and the bonding and reinforcing action Will be greatly enhanced. 40

When the matrix material has been placed in position over the metal plate or printing surface, which is to be reproduced, the edges of the plastic sheet 2 are bounded by strips 4 of a semihard compressible material, such a-s wood, and 5 these strips are of a depth slightly greater than the depth of the composite material to be moulded. After the strips are placed in position stop members which are here shown in the form of metal bars or strips 4 are then placed alongside the strips 4, being of lesser thickness than either the strips 4 or the plastic sheet 2 and the platen ram of the press is operated to rst engage the strips 4, and compressing same, it locks them 55 tightly to form limiting bounds for the rubber or other more compressible material placed over the printing surface.

The continued application of pressure iiattens 5 out the boundary strips and then applies pressure to the rubber material placed over the printing surface. The applied pressure compresses the surface of the rubber material into the interstices in the metal printing surfaces, also compresses the entire body of the reinforced mould material to a predetermined thickness as determined by the limiting stop engagement of the members 4 with the platen, so that the whole forms a hard, though flexible, rubber mould,

l5 which is cured under the application of heat. and pressure.

When the pressure is released the mould is removed from the metal surface and Where undercutting occurs in the metal plate, or where there are rough edge surfaces, the resilience of the cured rubber permits it to be stripped from the metal without distortion or injury.

The arrangement of the bounding strips in the press is quite important, as it prevents the soft compressible material from being squeezed out laterally, and ensures that the pressure is uniformly applied throughout the mass, and a reproducing surface of excellent quality is moulded in the face of the rubber material.

When the mould has been thus formed, a sheet of unvulcanized rubber material of a suitable quality to act as a printing surface is placed over the mould, which is placed in a suitable `press which is operated to apply a pressure suicient to force the unvulcanized rubber to iiow into Yt-he interstices formed in the mould. Suiiicient heat is applied to effectively vulcanize the rubber material compressed into the .mould cavity and an accurate flexible replica of `the original metal io plate or type surface is produced.

What I claim as my invention isi- 1. A method for producing non-metallic printing plates, consisting in first preparing a printing surface, then preparing a rubber material having i5 non-expansible non-shrinkable fibres embedded therein, then covering said printing `surface with the prepared rubber material, then placing around the material placed over said printing surface a compressible barrier, then pressing a plate first 5, to engage said barrier to hold it in a xed position and then to apply pressure to the rubber mass covering the printing plate, then applying heat to vulcanize the rubber in the mould being formed, then removing the mould, then compressing rubber into the mould so formed to for-m a printing plate and vulcanizing same.

2. A method of producing rubber printing plates, consisting in preparing a metal printing plate, then placing against the printing face thereof a sheet of unvulcanized rubber having embedded therein means for holding the rubber when vulcanized from expansion under vulcanizing heat and pressure, then placing strips of a compressible non-flowing material thicker than said rubber sheet to sluround the edges of said sheet, then pressing a flat surface to rst engage and compress said strips to hold them in a xed position and to then engage the rubber sheet and compress same to receive an accurate impression of the printing surface of said plate, applying heat concurrently with the pressure to rst flow and then vulcanize the rubber to form a nonstretchable mould, then placing rubber on the face of the mould and compressing and vulcanizing same to form a printing plate.

3. A means expressly for the production of rubber printing plates comprising, a mould formed of a single block of rubber composition of uniform texture and hardness throughout having a recess formed in the face thereof With a positive impression of a negative metal printing plate, said mould having reinforcing fibres incorporated uniformly throughout the entire mass of the mould and also having embedded therein a perforate metal sheet gripping the rubber and interlocking with the uniformly incorporated bres to hold the mould throughout its entire area against expansion under the applied heat and pressure for the purpose of facilitating the moulding of accurate rubber printing plates therein.

4. A method of producing rubber printing plates, consisting in preparing a metal printing plate, then placing against the print-ing face thereof a sheet of unvulcanized rubber having embedded therein means for holding the rubber when vulcanized from expansion under vulcanizing heat and pressure, then placing strips of a compressible non-flowing material thicker than said rubber` sheet to surround the edges of said sheet, placing non-compressible stop members on the outer side of said compressible members and of a lesser thickness than the latter, then pressing a at surface to first engage and compress said strips to hold them ina fixed position and to then engage the rubber sheet and compress same to the limit permitted by said stop members to receive an accurate impression of the printing surface of said plate, applying heat concurrently with the pressure to rst ow and then vulcanize the rubber to form a non-stretohable mould, then placing rubber on the face of the mould and compressing and vulcanizing same to form a printing plate.

ORBY B. CROWELL. 

